In Situ STM and AFM Study of Protoporphyrin and Iron(III) and Zinc(II) Protoporphyrins Adsorbed on Graphite in Aqueous Solutions

N. J. Tao, G. Cardenas, F. Cunha, Z. Shi

Research output: Contribution to journalArticle

81 Scopus citations

Abstract

Iron(III) protoporphyrin(IX), zinc(II) protoporphyrin(IX), and protoporphyrin(IX) have been studied on the graphite basal plane in aqueous solutions with both scanning tunneling (STM) and atomic force (AFM) microscopies. Real-time images directly show that the molecules adsorb onto the electrode and condense into monolayer films starting from small islands. In the monolayer films, all three molecules lie flat on the surface and form identical two-dimensional lattices with a = 13.4 ± 0.2 Å, b = 12.2 ± 02 Å, and y = 68 ± 2°. The corresponding molecular packing density is 1.1 x 10-10 mol/cm2, which is in excellent agreement with the value determined from cyclic voltammograms. Although the three molecules are nearly identical in their geometrical structures, their internal structures revealed by STM are significantly different. After the monolayer is completed, iron(III) protoporphyrin(IX) forms aggregates with a thickness of ∼8.5 Å, while zinc(II) protoporphyrin(IX) and protoporphyrin)IX) do not.

Original languageEnglish (US)
Pages (from-to)4445-4448
Number of pages4
JournalLangmuir
Volume11
Issue number11
DOIs
StatePublished - Nov 1 1995
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

Fingerprint Dive into the research topics of 'In Situ STM and AFM Study of Protoporphyrin and Iron(III) and Zinc(II) Protoporphyrins Adsorbed on Graphite in Aqueous Solutions'. Together they form a unique fingerprint.

  • Cite this